Storage drums of the type to which this invention pertains are commonly employed by industry because they are relatively easy to clean and normally are reusable. In general, such drums have a semi-cylindrical bead rim about their upper ends and closure lids having a mating peripheral lip which fit over the drum bead and an intervening gasket seal. An annular split metal closure ring is posed over the lid's lip and drum bead and then compressed radially to bring the ends of the ring in near abutting relation to secure the lid in place and compress the gasket seal. This effects a seal between the drum and lid. Typically a pair of locking lugs or clamp members are welded to the ring, one on either side of the split therein, so that they extend substantially radially outwardly of the ring. The mounted lugs or clamps have openings for passage of a tie bolt therethrough. In some instances, a threaded nut is associated with one of the lugs to engage the outer end of a threaded tie bolt and in other instances the opening in that lug is internally threaded to engage the bolt threads. In either instance, preferably the opening in the other lug is enlarged and unthreaded for free passage of the tie bolt. Appropriate threaded movement of the bolt serves to tighten the bolt connection between the lugs and coaxially align the lug openings to accordingly compress the ring and effect the sealed connection between the lid and drum.
Because the lugs in such closure assemblies protrude radially from the exterior of the annular ring and must align parallel or nearly so when the ring is closed, it is essential when the open ring is mounted for closure over the lid's lip and drum bead that the tie bolt have adequate radial clearance to align with and engage the threads associated with the second lug. Thus, the need for a larger diameter opening through the unthreaded lug. As the tie bolt is tightened, the two lugs approach one another to assume a parallel condition when the ring is closed. This typical closed condition creates an undesirable radial clearance between the body of the bolt and the walls of the opening through the unthreaded lug.
Recently, new packaging standards have been adopted by the United Nations requiring compliance with certain vibration, drop and hydrostatic tests to insure that drum containers of the order to which this invention pertains remain secure and leak proof during transit. However, because of the excess radial clearance between the tie bolt and the enlarged opening through the one unthreaded lug as above outlined, the ends of the closed split ring are prone to radial separation and movement under impact. This results in ring distortion and seal failure in most instances causing leakage, ultimate container failure and possible contamination of its contents.
The present invention is addressed to a solution of the aforedescribed problem.